Field of the Invention
The present general inventive concept is directed to a method and apparatus, and directed to a guided check valve.
Description of the Related Art
Spring operated check valves which can be used in high pressure hydraulic systems and in other applications are known in the art. FIG. 1 is drawing of a prior art thread-in disc type check valve.
In typical operation, this valve allows flow in one direction, while it prevents flow in the opposite direction. The valve shown in FIG. 1 consists of a valve body 101, valve disc 102, valve seat 103, and spring 100. Aperture 111 leads to a spring chamber 104. Outlet face 110 is the face of the valve on the outlet side (the side of the valve fluid flows out of). Nine holes are shown in the outlet face 110 through which the fluid flows. Inlet face 115 is the face of the valve on the inlet side (fluid flows into the inlet face side when the valve is open, through the valve and out the outlet face side).
In the absence of any fluid pressure, the valve disc 102 is urged in the closed position against the valve seat 103 by the spring 100. The mating surfaces of both the disc 102 and the seat 103 are flat lapped in order to provide a metal on metal seal.
FIG. 2 is a drawing of a cross section of the thread-in disc type check valve in the closed position. In this position, flow through the valve in the reverse direction, from leftward (the outlet face 110) to rightward (the inlet face 115), is prevented. In actual use, the forward face of the seat of the valve is typically provided with an O-ring to prevent any helical leakage around the threads from bypassing the seat/disc interface. One of the holes 112 is shown which allows fluid to pass through. Note that in the closed position, fluid cannot pass through the entire check valve in either direction, as the seal between the seat 103 and the disc 102 does not allow pass-through (and there is no other pass in the valve to allow such flow).
FIG. 3 is a drawing of a cross section of the thread-in disc type check valve in the open position. This occurs when the pressurized fluid, acting over the exposed face of the disc 102, creates a force sufficient to overcome the opposite closing force of the spring. Once the disc is lifted off of the seat, a flow path exists through the valve, from right to left. Fluid can flow out of the hole 112, which is one of many such holes (see FIG. 1).
“Disc flutter” is one disadvantage of this type of valve that can occur in certain flow conditions. The unguided disc is vulnerable to rapid motion, or fluttering, in the face of a turbulent flow through the valve, with the valve in a partially opened position. This can occur if the entrance to the valve is immediately downstream of a sudden change in fluid direction, such as after an elbow. This fluttering will cause the hardened disc to strike the valve body and seat at an inclined attitude (reflected in FIG. 4), resulting in very high local stresses, plastic deformation, and wear. Note how the disc 102 is at an angle. Also, frequent valve opening and closing in the face of a non-axial fluid flow, again, for example, caused by placement after an elbow or the like, and at nominal flows near or at the flow rating of the valve, can cause angular impingement of the disc against the body (as the valve is opening), and the seat (as the valve is closing). This again results in very high local stresses at the initial contact point, with resulting plastic deformation and wear.
The end result is that a disc type check valve operating under conditions conducive to valve disc flutter may experience accelerated wear, and its disc-seat interface may become incompetent in very short order. Disc chatter is another disadvantage of the disc type valve, where, when, at very low flow rates, it ‘chatters’ or rapidly opens and closes. This can cause rapid wear of the seat.
What is needed is a disc type check valve that overcomes, reduces or eliminates this disc flutter and chatter.